If I'm correct he's curretly an Avenger in the comics. But I think they should wait a while to make DD a member in the comics. Not because I'm an Avenger purist either, itd be like the comics where it took a while for DD to be convinced to become an Avenger.

DD spent far more time as a Defender than as an Avenger (he only got his Avenger card in 2011), but it's unlikely we'll ever see that team get together any time soon.

I definitely want to see DD join the MCU, but I really don't think Avengers is the way to go. He's a lone wolf, and does not play well with others. I'd much prefer to see him get a TV series or a rebooted movie franchise.